Vehicles driven by both an electric motor and an internal combustion engine are currently known and used and commonly referenced as hybrid vehicles. These hybrid vehicles use a combination of the electric motor and the internal combustion engine to power the vehicle's drive train so as to minimize the use of carbon-based fuels.
The electric motor is operable to perform in a driving state and a charging state. In the driving state the electric motor supplies power to the vehicle's drive train so as to move the vehicle. In the charging state the polarity of the electric motor is modified. Thus, the electric motor in essence becomes a generator slowing the vehicle and simultaneously building a charge. The charge is then supplied to the battery.
Some hybrid vehicles have a cruise control system. The cruise control system is operable to actuate the electric motor between a driving state and a charging state so as to maintain a selected speed. In operation the cruise control actuates the electric motor in the driving state so as to supply power to the drive train and accelerate the vehicle to the selected speed. When the vehicle exceeds the selected speed, the cruise control actuates the electric motor in the charging state.
In the charging state, the polarity of the electric motor is modified, and some cases reversed. Modification of the electric motor's polarity causes resistance to the drive train and slowing the vehicle down until the vehicle returns to the selected speed. As the polarity of the electric motor is modified, not only is the vehicle slowed down, but an electric charge is generated. The electric charge is discharged to the battery so as to charge the battery. Thus, utilizing the electric motor to help slow the vehicle down may also replenish the battery. This process is commonly referred to in the art as regenerative braking.
With reference now to FIG. 1, diagram of a system representing a current hybrid vehicle is provided. In instances where the battery is fully charged it may not be desirable to reverse the polarity of the electric motor and charge the battery further. As is known to those skilled in the art, over-charging a battery may reduce the life of the battery, as well as the battery's performance.
Thus, it is currently known to disable the cruise control when the battery is fully charged so as to prevent the electric motor from supplying excess charge to the battery. In such instances, reduction of the vehicle's speed is accomplished solely by mechanical braking. Further, the driver must reactivate the cruise control.
Accordingly, it remains desirable to have a system that allows for the cruise control to remain engaged when the battery is full and the vehicle has exceeded the selected speed, without over-charging the battery.